NRE when changing camera data provider profile values

[FejZa]

XRTK - Mixed Reality Toolkit Bug Report

Describe the bug

Changing values in a camera data provider profile throws a null reference exception in BaseCameraDataProvider.Disable()

To Reproduce

• Open a project and checkout latest XRTK development branch
• Change a value, e.g. default head height, in a camera data provider profile

Expected behavior

Value changes and is saved without a NRE.

Actual behavior

Value changes and is saved but NRE thrown and logged in console.

Your Setup

• Windows 10
• Unity 2019.1.14f1
• XRTK development (v0.2.0 preview)

Additional context

Object reference not set to an instance of an object
  at XRTK.Providers.CameraSystem.BaseCameraDataProvider.Disable () [0x00008] in D:\Projects\XRTK-Core-2\XRTK-Core\Packages\com.xrtk.core\Runtime\Providers\CameraSystem\BaseCameraDataProvider.cs:203 
  at XRTK.Services.MixedRealityToolkit.DisableAllServices () [0x00028] in D:\Projects\XRTK-Core-2\XRTK-Core\Packages\com.xrtk.core\Runtime\Services\MixedRealityToolkit.cs:1570 
UnityEngine.Debug:LogError(Object)
XRTK.Services.MixedRealityToolkit:DisableAllServices() (at Packages/com.xrtk.core/Runtime/Services/MixedRealityToolkit.cs:1574)
XRTK.Services.MixedRealityToolkit:ResetProfile(MixedRealityToolkitRootProfile) (at Packages/com.xrtk.core/Runtime/Services/MixedRealityToolkit.cs:119)
XRTK.Editor.Profiles.CameraSystem.<>c:<OnInspectorGUI>b__19_0() (at Packages/com.xrtk.core/Editor/Profiles/BaseMixedRealityCameraDataProviderProfileInspector.cs:116)
UnityEditor.EditorApplication:Internal_CallDelayFunctions()